linux-kernel - Re: "dma-mapping: remove CONFIG_DMA

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Date:   Wed, 30 Mar 2022 15:17:20 -0400
From:   "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        regressions@...ts.linux.dev
Subject: Re: "dma-mapping: remove CONFIG_DMA_REMAP" causes AMD SME boot fail

Excerpts from Christoph Hellwig's message of March 30, 2022 2:01 pm:
> Can you try this patch, which is a bit of a hack?
> 
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 50d209939c66c..61997c2ee0a17 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -28,7 +28,8 @@ bool force_dma_unencrypted(struct device *dev)
>  	 * device does not support DMA to addresses that include the
>  	 * encryption mask.
>  	 */
> -	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {
> +	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT) &&
> +	    !get_dma_ops(dev)) {
>  		u64 dma_enc_mask = DMA_BIT_MASK(__ffs64(sme_me_mask));
>  		u64 dma_dev_mask = min_not_zero(dev->coherent_dma_mask,
>  						dev->bus_dma_limit);
> 

This seems to work for me.

Cheers,
Alex.